Coarsely chop chocolate chips. In baking dish, toss bread and chocolate. In large bowl, with wire whisk or fork, beat eggnog, Half & Half, sugar, and eggs until well mixed. Pour eggnog mixture over bread and chocolate; dot with butter. Set baking dish in large roasting pan; place on middle oven rack. Fill roasting pan with hot water to come halfway up side of baking dish. Bake bread pudding 1 hour or until knife inserted in center comes out clean. Sprinkle with powdered sugar. Serve pudding warm.